Protein-driven lipid domain nucleation in biological membranes

Lipid rafts are heterogeneous dynamic lipid domains of the cell membranes that are involved in severalbiological processes, such as protein and lipid specific transport and signaling. Our understanding of lipid raftformation is still limited due to the transient and elusive nature of these domains in vivo, in contrast with thestable phase-separated domains observed in artificial membranes. Inspired by experimental findings highlightingthe relevance of transmembrane proteins for lipid rafts, we investigate lipid domain nucleation by coarse-grainedmolecular dynamics and Ising-model simulations. We find that the presence of a transmembrane protein cantrigger lipid domain nucleation in a flat membrane from an otherwise mixed lipid phase. Furthermore, we studythe role of the lipid domain in the diffusion of the protein showing that its mobility is hindered by the presenceof the raft. The results of our coarse-grained molecular-dynamics and Ising-model simulations thus coherentlysupport the important role played by transmembrane proteins in lipid domain formation and stability.